[Linux-cluster] Using cman,etc for a non-gfs app

[Patrick Caulfield]

Lon Hohberger wrote:
> On Thu, 2005-06-23 at 11:23 -0400, Olivier Crete wrote:
> 
> 
>>>If you use CMAN's service manager, you will be able to tell if the app
>>>has crashed (all nodes in that service group will be notified of the
>>>state change).
>>
>>In the RHEL4 branch there does not seem to be a userspace API for the
>>Service manager.. apart from the ioctl and libmagma. Is libmagma your
>>long term api ? Also, can libmagma be used in non-GPL apps? I saw some
>>scary comments in magmamsg.h... 
> 
> 
> Correct.
> 
> libmagma is LGPL.  The theory is that you could write any app and link
> it dynamically against it.  Furthermore, the idea was that, on the
> back-end, you could make it load a non-Free plugin to talk to a non-Free
> cluster infrastructure.
> 
> libmagmamsg is GPL, due to having code chunks from an older GPL project.
> The code is quite awful, but it works.  I hope it gets replaced with an
> nice cluster-agnostic message system at some point which can be used for
> more than just cluster stuff.
> 
> 
>>>Internal deadlocks are harder to detect from the cluster infrastructure
>>>perspective.  I'd consider using the kernel watchdog timer.
>>
>>An easy way would be to have a cluster watchdog (ie.. the app must
>>"ping" the cman daemon at least one in X seconds and if it isnt its
>>considered deadlocked..)
> 
> 
> As it stands now, kernel-mode cman doesn't have this kind of capability.
> I could be mistaken, of course.

cman manages nodes, not applications.

-- 

patrick